Earth boring tool with rolling cutters



Aug. 1l, 1936. J. A. ZUBLIN I EARTH BORING TOOL WITH ROLLING CUTTERSFiled DeC. 26,' 1955 2 SheeiZS-Sheetl l Aug 11, 1936. J. A. ZUBLIN2,050,989

EARTH BORING TOOL WITH ROLLING CUTTERS Filed Dec. 26, 1935 2Sheets-Sheet 2 gmc/who@ Patented Aug. ii, iosa CUTT . 2,050,989 y EARTHcome Toor. wrm noa aas John A. zutun, Los angela, cani. l ApplicationDecember 26, A1935, Serial No. 56,252

6 Claims.

penetration, it is necessary to have only a mini-A` mum portion of thecutters in contact with the f formation at any time, as higher pressureper l unit area increases the penetration of the teeth. On the otherhand, to keep the cost of drilling within lreason by giving a long lifeto the bit, it is necessary to providev a maximum of cutting lteeth onthe bit' since the drilling life of a bit 2o is generally proportionalto the total number and size of `cutting teeth available to cut theformation; and an increase in the total number of teeth has usually beenaccompanied by a like increase in the number of teeth cutting at any 25one time.

It is thus apparent that the ideal bit has a large total amount ofcutting surface but has only a veryfpsmall part of that surface active,or in drilling contact, at any one time, the re- 30 mainder of thecutting surface being, in effect in reserve, since it also does itsshare of the cutting after the first active portion moves out of contactwith the formation. In roller or cone bits of the present types, all theroller or 35 cone cutters are in simultaneous engagement with theformation, so the reserve cutting surface is limited to that portion ofeach cutter not so engaged, and amounts to but a few, perhaps three tosix, times the active cutting sur- 40 face, whereas' both the elciencyand the life vof the bit would be increased by increasing the ratiobetween the reserve and active portions of v the cutting surface.

Another disadvantage of the conventional roll- 45 er or cone bit havingbut a small number of rolling cutters is that each cutter rolls in thesame definite path concentric to the bit axis as the bit is rotated.Since often only one cutter, and rarely more than two cutters, cover agiven 50 areafthe failure of one or two cutters holds up the entire bitwhen there is no additional cutter to perform cutting operations in thearea covered by the broken rollers or cones.

Thus it is a general object of my invention 55 both to decrease theamount of active cutting (Cl. Z55-71) arca which is at any one time incutting position, and to increase the amount of reserve area. Thesechanges have the effect of increasing the speed of penetration,` andalso of lengthening the bits life since there is more aggregate cut- 5ting surface to be Worn. l

It is also an object of the invention to provide a bit which not onlyhas the usual reserve cutting area on each cutter, but also has asumciently large number of cutters that several entire cutters are inreserve, and, as a whole, are each successively brought into cuttingposition and then returned to the reserve or non-cutting position. Byhaving entire cutters in reserve, the ratio between reserve" and activeporl5 tions of the aggregate cutting surface is increased to severaltimes that possible when all cutters are simultaneously in contact withthe formation.

A further object of the invention is to provide a bit having a pluralityof cutters which are moved over varying paths non-concentric relative tothe bore hole center, so that all cutters eventually move acrosssubstantially all points on the hole bottom and the complete failure ofone cutter does not prevent removal of vformation at any point.

Another object is to provide a bit having the above characteristics inwhich the roller cutters contact the formation with a substantially truerolling motion throughout all, or substantially all, of their engagementwiththe formation, thus disintegrating the formation with a crushingaction.

Another object is to provide a bit in which the cutters are movedsuccessively from cutting position upward to a position where they arecleaned by the circulation uid and then returned downwardly to thedigging position.l

These objects are attained in the bit of my invention by providing thebit shank, which is attached to the string of drill pipe for rotationthereby about a vertical axis, with'a Wheel-like cutter carrier mountedto rotate in a plane which is preferably vertical or .generally so.Around the periphery of this cutter carrieris mounted a plurality ofrolling cutters of any suitable type which extend radially beyond thecarrier, and, as the carrier revolves, are brought successively intodrilling contact withthe earth formation to be cui; away. The individualcutters are preferably, though not necessarily, mounted so that theiraxes of revolution areslightly inclined to the plane or revolution ofthe carrier, so that not only is the motion of the cutter over theformaseated it is rotated slightly to theposition shown in Fig. 1, wherethe lug is engaged by the inner I'in which:

. Fig. l is a side elevation of a. bit constructed according to myinvention; y

Fig. 2 is a vertical section through the bit on line 2-2 of Fig'. 4,showing the cutter' carrier in elevation;

Fig. 3 is a front elevation of the bit as 'viewed from the left of Fig.l; l y

Fig. 4 is a horizontal section of the bit on line 4--4 of Fig. 2, butrotated 90 to the right;

Fig. .5 is a vertical section through a variational form of bit havingtwo cutter carriers;

and,

Fig. 6 is a-section on line 6-6 of Fig. 5.

There is shown in Fig. 1 a bit provided wit a shank, indicated at III,having on its upper 'end threaded pin II by means of which the shank isattached to a string of drill pipe or drill stem for rotation therebyabout a vertical axis. The lower portion of the shank is formed with twodepending legs I2 which carry horizontal bearing shaft I4. On the backside ofthe bit, legs I2 are preferably joined by an integrally formedhood I5, advantages of which will be later mentioned.

The horizontal* shaft I4 is preferably non-rotatably mountedon theshank-and forms a bear- .ingl for the wheel-like cutter carrier I8 whichis mounted to rotate relative .to the shank and in a vertical plane. Toreduce friction and allow the carrier to turn more freely, there may beprovided 'roller bearings 9 between shaft I4 and the carrier, and ballbearings 2li for taking the thrust between the carrier and the shankbody. Inorder to securely hold bearing I4 in position after the bit isassembled, it is provided with some lockingA means which may takevarious forms, though it is here shown/as comprising a fixed lug 2|extending radially nearone end of shaft I4 and adapted to be received inan L- shaped slot 22 in one leg |2'of the bit. .As shaft I4 is insertedaxially, lug 2| enters the horizontal end of slot 22, 4and when theshaft is-properly vertical end of slot 22 and the bearing is heldagainst axial movement., When the bearing is in this position, atransverse hole 23 in the opposite end of bearing I4 is brought into ahori- -zontal-positionand aligned with a similar bore 24in the shank sothat locking pin 25 maybe inserted through bores 24 and'23 to holdbearing I4 against rotation. The shank is provided with a recess at 25,intermediate the ends of pin 25 so that by striking that portion of thepin exposed in the recess a sharp .blowthe pin is bent as shown in Fig.4 to prevent its longitudinal displacement from bore 24. 'l

As may be seen from Figs. 2 and 4, cutter carrier I8 is provided with 'aplurality of radial slots 28-spaced about its circumference. In each ofthese radial slots there -is placed a cutter 30, of any suitable-type,mounted to rotate on a pin 3|.

body to hold them in place, the ,welds being indicatedat 32.

Rolling cutters 3|) may be of any desired size or shape and have anysuitable toothformation, but are here shown as having teeth extendingparallel to the axis of cutter rotation, while the cutters themselvesare arranged in two parallel rows of eight cutters about the peripheryof the cutf ter carrier, the rows beingstagg'ered, that'is, the cuttersof' one row occupy the intervals between cutters of the other row, asshown in Figs. 2 and 3. Cutters 30 lie substantially entirely betweenthe parallel, vertical sides of carrier I8, or between the sidesprojected, but extend radially beyond the `carrier in order to contactthe earth formation to be drilled. 'As may be seen from Fig. 1, thehorizontal axis of bearing I4 passes to one side of the vertical axis ofthe bit 'so thatf engagement of the cutters with the formation takesplace only on that one side of the bitsvertical axis.

Cutter bearing pins 3| are preferably not placed at right angles to theaxis of rotation of the cutter carrier but are slightly inclined to thesides'of the carrier, as may be seen in Fig. 3, soV

that the cutters ,rotate about axes always slight- 1y inclined to thevertical plane of carrier vrevolution. The cutters yare inclined in thismanner so that they will cause the carrier to revolve by their movementover the formation. From Fig.

1 it will be seen that the cutters i'lrst contact the.

formation at a point substantially level with the axis of bearing I4,that is with the center -of the carrier, and that .by revolving shankII) in a clockwise manner about its vertical axis, the cutters as theycontact the formation will ref `volve about their own axes so as to moveover the formationwith a true rolling motion. As the cutters seen inFig.3 initially engage the formation they tend to roll in a pathdownwardfrom the vertical of their axes of revolution, .as

described above, and they continue to roll on `the axis of bearing I4,when they arevmoved out of engagement with the formation, -as will beclearly seen from Fig. 1. Because the teeth tend .to follow thisdownwardly inclined path rather" than a horizontal path, the downwardcomponent -.of the cutter motion causes the cutter carrier to lyinclined to the left because of the inclination revolve in acounter-clockwise directionas viewed in Figs.` 1 and 2, and thisrotation of the carrier brings the successive cutters into contact withthe formation and, after they have reached the bottomof the hole, movesthem successively out of engagement with the formation.

The directipn of rotation of carrier I8 is determined by thee directionof inclination of cutters 30. The cutters are preferably inclined asshown in order -to produce counter-clockwise revolution of -thecarrier'since this permits the cutters to operate during a downward'movement over the formation. If, however, the inclination of thecutters were. reversed and the shank rotated in -the same directionabout its vertical axis, .then

the carrier would move in a clockwise direction,

as viewed. in thedrawings, withjthe cutters'initiallycontacting theformationat the bottom of the hole and rolling upwardly while cutting.-It will also be realized that the speed of rotation of the carrier, andconsequently the path of the cutters, may be varied by changing theinclinationof the cutters to the plane of car-- rier revolution.

In order to prevent in the bit with the cutter carrier reversed so t thecutters have the opposite inclination` from' that shown, the borethrough the carrier is made with two dierent diameters and bearing l@ isprovided with a step as shown in Fig. Li. Thus the bit can only beassembled with the parts in the proper relationship'.

, The exact path followed by any given cutter will Vary according to thespeeds of rotation of the shank and the cutter carrier, but in generalthe path commencing at the point of initial con tact will be a spiralfollowing the surface ci the formation and decreasing in radiusdownwardly to the point beneath the center ci the carrier where thecutter ceases contact with the torinaa tion. The cutters do not roll onany fined path concentric with the center ci thehole and do not tend tofollow a preceding path; Consenuent= ly the ailure or loss oi one or twocutters will not stop the hit from drilling, since it is only e questionci time until other cutters will go over those portions ci the holewhich would have heen The upper end ci shank t@ is formed with aninternal fluid passage 35 which receives circula= tion fluid from thedrill stern, and this passage is provided with two discharge outlets 3Sand 3l whici'i direct a stream ci uid against the cutters as they aremoved upwardly troni digging position and returned to their point ciinitial lose tion contact. Passages 36 and Stare inclined oppositely inorder to clean both sides ci the cutters, and hood i5 confines thestream issuing from passage Si so as to aid the cleaning action.

From this construction it will he seen that not only has each rolleronly a portion ci its teeth active or in cutting engagement at any giventime with the remainder ci the teeth in reserve or non-cutting position,but that the hit as a whole has only a portion of its cutters active atany time and has a large reserve ci entire cutters which are in thenonecutting msition. le the proportion oi the total cutters which isactive or engaged with the formation will vary with the number ofcutters and their arrangement on the carrier yet it will he eeen irontthe construction oi the bit that the nurnher ci active cutters will, 'ingeneral, always be lees than onehaii? of the total number oi cutters. Enthe Ecrin illustrated, there are eight cutters in each ci* two rowsmaking a total of sixteen cutters, of which only ve are active at onetime so that the number in reserve is approximately twice the number ofactive cutters.

A variational form of bit um .z g these e principles o operation, isshown in Figs. 5 and t.

The strani; ita has a pair ci integra toed bearings on' opposite sidesci the shank, each cutter carrier ita which revclv` about pin-it in aplane inclined thereto. The cutter carrier has a central boreformed'with a cuestion ci from the spirit and scope of the invention,and

, -described and cljaed herein..

conical and cylindrical hearing surface which Y are complementary to andengage respectively `the correspondingsurftu, lli on the shank.

' through a passage t@ in the carrier body, screw it being placed in thepassage to keep the balls in place.

Shank. ita has an internal passage it for cir@ culation iuid thatdischarges from a central orihce il against the rolling-cutters in theirbottoni position. Auxiliary passagesl@ conduct uidl l5 from the mainpassage to 4'the bearing laces tor lubrication purposes.

Like carrier itl, carrier ita has a plurality' of radial slots 28 eachof which has a cutter 3@ rotatahly mounted on a pin 3l. However, thecarrler tec has only a single row 'of cutters, there being two suchcarriers to provide the same number of cutters as in the hit'firstdescribed.

.The cutter hearings 3i are placed at right angles to the axis cicarrier rotation and all lie in a single plane parallel to the plane ofcarrier revolution. From Fig. 6 it will be seen that the cutters i'lrstcontact the formation at points horizontally opposite the carrierbearing. When the bit rotates clockwise, as viewed in Fig. 6, thecutters are in the same position relative to the sides of the well hereas the cutters of Fig. il; and

A the two carriers will revolve, oppositely relative to eachother. Thecuttingacton is as described shove, each cutter traversing a downwardlyin# cli'ned spiral path over the formation. Since the cutters on the twocarriers contact the Well bore 'at diametrically opposed points (Fig. 6)each so placed on the hit that they roll over the orrna- 45 -tion inespiral path, since each axis ci cutter revolution is inclined to thevertical when it contacts the formation horizontally opposite thecarrier axis. i This positioning ci the cutters is effected byplacingthe various axes of revolution 5o in cer relationships to one another.fr rctationaleaxis ol the bit shank may be considered as remainingvertical. The `rotational axis of the cutter carrier is then preferablyperpendicular either to the shank axis or to the cutter axis and isinclined tothe other one ci these two axes. l Having descrlbed'variousMiri. oli-my invention, it will be clear how various other embodimentsmay be constructed without departing therefore the annexed claims are tobe considered as illustrative ci rather than restrictive upon y thebroader aspectsof my invention.

Attention is directedto my copending application Ser. No. 71,60@ filedrch 30, 1936. o5 rvhereinli have generic claims covering the species J Iclaim as my invention:

l. In a rotary-earthboring tool, thecornbination of a shank adapted tobe rotated about `a. 7o vertical axis by a drill stem; a cutter carrierrotatably mounted on the shank; and a plurality oi -individl cuttersmounted on the cutter carrier lor succsive intermittent cutting sont wr'the formation rotation or the 76- Y carrier rotatably mounted on theshank to revolve in a vertical'plane about a horizontal axis; Vand aplurality of circumferentially spaced individual cutters rotatablymounted on the cutter carrier y andbrought successively intointermittent cutting contact with the formation by rotation of thecarrier, said cutters being mounted to rotate about axes which areinclined with respect to the vertical plane of revolution of the carrierso that the cutters rolling over the formation follow a spiral path andcause the carrier to rotate as the shank is rotated about its axis.

4&0 cutter carrier for successive intermittent cutting 3. In arotary'earth boring tool, the combina'- tion of a shank adapted to berotated about a vertical axis by a drill stem; a cutter carrierrotatably mounted on the shank to revolve about a second axis; and anindividual cutter rotatably mounted on the periphery of the carrie'' torevolve about a third axis, and' brought into intermittent cuttingcontact with the formation upon rotation of the carrier'Y the rotationalaxis of the carrier being perpendicular to one ofsaid two other axes andinclined to the remaining axis. y

4. In a'rotary earth boring tool, the combination of a shank adapted tobe: rotated about a vertical axis by a drill stem; a cutter carrierrotatably mounted on the shank; and a plurality of individual cuttersrotatably -mounted on the contact with the formation upon rotation ofthe carrier; the axes of rotation of the carrier andof the individualcutters being so disposed that as'the shank rotates, each cutter as itrolls over the formation traverses a generally spiral path which-'isinclined downwardly from a point substantially level with the center -ofthe carrier to a point substantially directly beneath the center of thecarrier, the vertical component of the cutter movement causing thecarrier to revolve.

- 5. In a rotary earth boring tool, the combination of a shank adaptedto be rotated about a vertical axis by a drill stem; a plurality ofcutter carriers rotatably mounted on the 'shank to revolve in generallyvertical planes about axes inclined slightly to the horizontal; and aplurality of individual cutters rotatably mounted on each of the cuttercarriers for successive intermittent digging contact with the formationupon rotation of the carriers; said cutters being mounted 4to rotateabout axes lying in the plane of rotation of the carrier upon which theyare mounted so that the cutters rolling over the formation follow aspiral path and cause the carrier to rotate as the shank is rotatedabout its axis.

6. In a rotary earth boring tool, the combination of a shank adapted tobe rotated about a vertical axis by a drill stem; a pair of bearings on-the shank, each bearing comprising thrust and journal bearing surfaces;a cutter carrier rotatably 'mounted on each of the bearings, saidcarrier having a central bore comprising bearing surfaces complementaryto and engaging the thrust and journal bearing surfaces of the shank;

-and a plurality of individual cutters rotatably mounted on each cuttercarrier for successive intermittent digging contact with the formationupon rotation of the carrier.

JOHN A. ZUBLIN.

